优化级别必需为s,其他优化级别也不会导致编译时出错，但会导致运行时出错。原因涉及局部变量分配堆栈处理方式不同，也就是OS_CPU_A.c那个文件中的移植部分。还有就是其他优化涉及的中断自动保存寄存器的数量有所出入。-Necessary to optimize the level of s, other optimization levels will not lead to compile-time error, but it will result in run-time error. Reasons relating to the allocation of local variables, stack processing in different ways, that is, OS_CPU_A.c that the transplanted parts of the file. There are other optimization related to the interruption of the number of registers saved automatically have access to.